This graph shows a significant increase in the number of glacial earthquakes in Greenland since 2002. In contrast, the number of earthquakes away from Greenland and north of 45° latitude has remained relatively constant. Glacial earthquakes are associated with the accelerating retreat of glaciers such as Kangerdlugssuaq in response to global warming.1

Key Facts

Kangerdlugssuaq glacier on the southeast coast of Greenland is retreating so fast that it has produced a class of earthquakes—known as glacialquakes—that can be measured by seismometers around the world.1,3

Kangerdlugssuaq glacier was responsible for nearly half of the 136 glacialquakes recorded from January 1993 to October 2005 in Greenland—far more than any other Greenland glacier.1

The frequency of glacialquakes has been rising since the late nineties, and has been growing particularly rapidly since 2003.1,3

An increase in glacialquakes signals accelerated movement of Greenland's glaciers, which both reveals the effects of global warming and is expected to contribute to future warming.9

Details

From 2000 to 2005, Kangerdlugssuaq glacier was the fastest-moving glacier on Greenland, retreating around eight to nine miles (13 to 14 kilometers) per year.2 The end (terminus) of the glacier not only retreated from the ocean but also thinned by more than 820 feet (250 meters) during that period.2

The rapid melting of Kangerdlugssuaq glacier has produced a special category of earthquake known as a glacialquake.1,3 Once thought to occur when glacial ice strikes solid earth beneath it, glacialquakes are now attributed to lurching that occurs when parts of the glacier break off (calve) into the ocean.4,5

Most common in Greenland, glacialquakes can be detected by seismometers around the globe.1,3 Of the 136 glacialquakes recorded from January 1993 to October 2005 in Greenland, Kangerdlugssuaq glacier was responsible for nearly one-half (61)—far more than any other Greenland glacier.1 Neighboring Helheim glacier (with 26) and Jakobshavn Isbræ (with 11) were second and third, respectively.1

Detecting glacialquakes is important because glaciers appear to accelerate after large calving events.2 The frequency of glacialquakes—which has been rising since the late 1990s—has increased particularly since 2002.3 In fact, the number of quakes in 2005 was twice that of 2001.1 In late summer of 2005, glacial seismic activity was almost five times greater than in the winter months—most likely owing to seasonal changes in temperature.1,3

Glacialquakes represent only a small portion of glacial motion.3 Scientists have observed many other effects of global warming on Greenland. Kangerdlugssuaq glacier, for example, has changed drastically since the beginning of the century.

The glacier remained relatively stable from 1960 to 2002, coinciding with cooler-than-average local summer temperatures through the mid-1990s.3 After local summer temperatures began to rise, around 1995, Kangerdlugssuaq's speed more than doubled, from an average of 49 feet (15 meters) per day in 2001 to 131 feet (40 meters) per day in 2005.6

During the same period, the terminus of the glacier thinned.2 The correlation of these glacial changes with rising temperatures implies that warming influences glacier motion almost immediately.1,2,7,8

The Global Context

An increase in glacialquakes signals accelerated melting of Greenland's glaciers, which both reveals the effects of global warming and is expected to contribute to future warming—amplifying the consequences in the Arctic region.9

The retreat of Kangerdlugssuaq, for example, may alter the amount of the sun's energy reflected back into space (known as albedo). The retreat exposes soil, rock, and ocean surfaces, which absorb light and heat, causing further melting.10,11 (See Jakobshavn Isbræ and Helheim glacier hotspots for more information on albedo.)

As icebergs from Kangerdlugssuaq break off into the ocean and melt, they add to rising sea levels. The rate at which the melting Greenland ice sheet contributed to global sea-level rise more than doubled from 1996 to 2006.2 (See Greenland ice sheet hotspot for more information on sea-level rise.)

Accelerated melting also adds more freshwater to the oceans, altering ecosystems and changing ocean circulation and regional weather patterns.9